1. Field of the Invention
This invention relates to venetian blinds and, in particular, to vertically arranged venetian blinds in which a plurality of elongated louvers are arranged vertically and are supported from the upper end by a louver carrier which, in turn, is supported by a headrail. In blinds of this type, means must be provided for traversing the carriers and their supported louvers along the rail to open and close the blind. Means must also be provided for rotating the louvers about their individual vertical axes. In many blinds of this type a separate means, such as a drive shaft, cord or chain, is provided for the traversing function and a second such drive is provided for the rotating function. In other blinds of this type, particularly in recent years, a single operating means has been provided to perform both the traversing and the rotating function. It is to this single operating mechanism-type of blind to which the present invention is particularly directed.
2. Prior Art
In the type of vertical venetian blind in which a single operating mechanism such as a drive shaft is used for both functions (traversing the blind and rotating the louvers) a disengagement or decoupling between the louver and the turning shaft must take place at the end of the turning range, at least to an extent sufficient to permit the drive shaft to rotate beyond that point in order to traverse the louvers to open or closed position of the blind. Heretofore, this decoupling of the louvers from the rotation of the drive shaft has involved very high engineering expenditure and complex slip clutches. Additionally, extensive wear of the slip clutches has been experienced due to the fact that even when slipping (decoupled) a considerable frictional force is still applied to the drive shaft, thus requiring a proportional increase in the input power to rotate the shaft.
Moreover, prior art devices have generally suffered from the problem that when rotating the louvers to adjusted position, there may remain a tendency to continue the transport of the carrier along the rail.